kernel: poll system and poll syscall

kernel-src/sys/syscalls/poll.c

@@ -0,0 +1,82 @@
+#include <kernel/syscalls.h>
+#include <kernel/file.h>
+#include <kernel/poll.h>
+#include <kernel/vmm.h>
+#include <logging.h>
+#include <kernel/alloc.h>
+
+typedef struct {
+	int fd;
+	short events;
+	short revents;
+} pollfd_t;
+
+syscallret_t syscall_poll(context_t *, pollfd_t *fds, size_t nfds, int timeoutms) {
+	syscallret_t ret = {
+		.ret = -1
+	};
+
+	// timeouts are not supported yet
+	__assert(timeoutms <= 0);
+
+	if ((void *)fds > USERSPACE_END) {
+		ret.errno = EFAULT;
+		return ret;
+	}
+
+	size_t fdsbuffsize = nfds * sizeof(pollfd_t);
+	pollfd_t *fdsbuff = alloc(fdsbuffsize);
+	if (fdsbuff == NULL) {
+		ret.errno = ENOMEM;
+		return ret;
+	}
+
+	memcpy(fdsbuff, fds, fdsbuffsize);
+
+	polldesc_t desc = {0};
+	ret.errno = poll_initdesc(&desc, nfds);
+	if (ret.errno) {
+		goto cleanup;
+	}
+	__assert(spinlock_try(&desc.lock));
+
+	size_t eventcount = 0;
+
+	for (uintmax_t i = 0; i < nfds; ++i) {
+		file_t *file = fd_get(fdsbuff[i].fd);
+		if (file == NULL) {
+			fdsbuff[i].revents = POLLNVAL;
+			++eventcount;
+			continue;
+		}
+
+		int revents = VOP_POLL(file->vnode, timeoutms == 0 ? NULL : &desc.data[i], fdsbuff[i].events);
+		if (revents) {
+			fdsbuff[i].revents = revents;
+			++eventcount;
+		}
+
+		fd_release(file);
+	}
+
+	if (eventcount == 0 && timeoutms != 0) {
+		// TODO timeout
+		ret.errno = poll_dowait(&desc);
+		if (ret.errno == 0) {
+			int fd = ((uintptr_t)desc.event - (uintptr_t)desc.data) / sizeof(pollfd_t);
+			fdsbuff[fd].revents = desc.data[fd].revents;
+			eventcount = 1;
+		}
+	}
+
+	memcpy(fds, fdsbuff, fdsbuffsize);
+
+	poll_leave(&desc);
+
+	ret.ret = eventcount;
+
+	cleanup:
+	free(fdsbuff);
+
+	return ret;
+}